Biochemical Studies on 5′‐Nucleotidase of Schwann Cells in Degenerated Nerve

Abstract: This report describes the partial characterization of 5′‐nucleotidase (5′‐AMPase) in Schwann‐cell plasmalemmae (PM) prepared from degenerated cat sciatic nerve. 5′‐AMPase was enriched 3.7‐fold in the PM fraction over that of the crude homogenate preparation. The plant lectin concanavalin‐A (Con‐A) reduced Schwann cell PM 5′‐AMPase activity in a concentration‐dependent manner (30‐600 μg/ml). Plasma membrane 5′‐AMPase activity was maximally inhibited to 20% of control values by Con‐A (400–600 μg/ml), and activity returned to control levels by pretreatment with the hapten sugar α‐methyl‐d‐mannoside (50 mM). Equimolar concentrations of UDP and ADP (100 μM) reduced the rate of hydrolysis of labeled AMP to labeled adenosine in PM to 45% and 35% of controls, respectively. This is the first study to characterize a Schwann‐cell PM enzyme and demonstrates that 5′‐AMPase may be used as a Schwann‐cell PM marker enzyme.